| Now that we have spent some time considering a generic UNIX kernel, the tools of the trade, and some of the challenges faced by the kernel designers, let's turn our attention to the specifics of the HP-UX kernel. The current release of the Hewlett-Packard HP-UX Operating System is HP-UX 11.i (the actual revision number is 11.11). We concentrate on the current release, but as many production systems are still running HP-UX 10.20 and HP-UX 11.0, where appropriate we try to cover material relevant to these releases as well. The HP-UX kernel is a collection of subsystems, drivers, kernel data structures, and services that has been developed and modified for the past 20 years. This legacy has yielded the kernel we present in this book. Over the years, virtually no part of the kernel has gone undisturbed: the engineers and programmers at HP have shown an unwavering commitment to the continuous process-improvement cycle that defines the HP-UX kernel. The authors of this book tip our collective hat to their continuing efforts and vision. In its current incarnation HP-UX runs primarily on systems built on the Hewlett-Packard Precision Architecture processor family. This was not always the case. Early versions ran on workstations designed on the Motorola 68xxx family of processors. As in the past when HP-UX was ported to the HP-PA RISC chip set, today we are on the threshold of another port of this operating system to an emerging new platform: the Intel IA-64 processor family. In this book, we concentrate on the HP PA-RISC implementation. | 